Hemiasterlin (I) was first isolated from the sponge Hemiasterella minor (class, Demospongiae; order, Hadromedidia; family, Henmiasterllidae) collected in Sodwana Bay, South Africa (see, Kashman et al. U.S. Pat. No. 5,661,175). It was reported that Hemiasterlin exhibited antitumor activity against several cell lines, including human lung carcinoma, human colon carcinoma and human melanoma.

After the initial isolation and reporting of this compound, additional hemiasterlins were isolated, and several hemiasterlin derivatives were synthesized and their biological activity was also investigated. It was subsequently reported that Hemiasterlins and certain analogs thereof exhibit antimitotic activity and thus are useful for the treatment of certain cancers (see, U.S. Pat. No. 6,153,590 and PCT application WO 99/32509). However, only a rather limited number of Hemiasterlin analogs were prepared, half of which were the natural products themselves, isolated from Cymbastela sp., or were obtained by modifications to the natural products. Thus the number and types of derivatives that could be prepared and evaluated for biological activity were limited.
Clearly, there remains a need to develop synthetic methodologies to access and examine the therapeutic effect of a variety of novel derivatives of Hemiasterlin, particularly those that are inaccessible by making modifications to the natural product. It would also be of particular interest to develop novel compounds that exhibit a favorable therapeutic profile in vivo (e.g., are safe and effective, while retaining stability in biological media).